Hello Margaret,
The 50W has a flow rate of 0-5000gph.
A 35W will be release in Dec/Jan. 2015
I'm expecting to see 35W samples end of the month beginning November but production models much later.
A larger 70W model and Batery back up for all models is expected some time in Q1/2015.
Maxspects Facebook Page will also have the latest info:
https://www.facebook.com/Maxspect